Influence of Beam Spot Size in Measurement of Pulse Waves at Multiple Parts of the Human Body Using Millimeter-wave Array Radar

This study evaluates the accuracy of measurements of cardiac pulse wave propagation using a 79-GHz millimeter-wave ultra-wideband multiple-input multiple-output array radar. The radar echoes from multiple parts of the human body were extracted using an array beamforming technique. The phase of each echo was converted to the skin displacement and its waveform was carefully compared with the waveform obtained using laser displacement sensors, which was used as a reference for evaluation of accuracy. Because the beam spot sizes of the radar and laser sensors were different, we applied smoothing to the waveform measured using the laser sensor, to make the effective beam spot size equivalent to the spot size of the array radar beam. We then quantitatively analyzed the relationship between body displacement waveforms measured using the array radar and laser sensors.